Drying southern pine at 240°F-- effects of air velocity and humidity, board thickness and density

Description

Kiln time to reach 10 percent moisture content was shortened by circulating air at high velocity, but was little affected by board specific gravity. A wet-bulb depression of 80°F. provided faster drying than depressions of 40 or 115°F. At 80° depression and with air circulated at 930 f.p.m.. kiln time was directly proportional to board thickness. Under these optimum conditions, 1 by 4's required 10.4 hours to reach 10 percent moisture content; boards 1.5 and 1.9 inches thick required 15.8 and 20.7 hours respectively. Total energy expended in drying to 10 percent moisture content was affected by board thickness and specific gravity; air circulation velocity did not significantly affect total energy. Boards kilned for 24 hours at 240°F. and then ovendried showed significant variation in shrinkage according to the drying schedule used. No significant differences in modulus of elasticity. proportional limit. modulus of rupture in bending, or toughness were detected in clear-wood specimens cut from lumber dried by the six schedules.